TABLE OF CONTENTS In the previous three chapters we discussed the nature of digital filter design. We are now ready to discuss the implementation of these digital filters. We begin this chapter with a discussion of several important issues in digital filter selection and implementation. These issues include the differences between real-time and nonreal-time implementation, as well as the effects of finite precision representation of input signals and filter coefficients. Then, we discuss the C code for implementing IIR and FIR filters. Efficient algorithms will be developed to increase the speed of execution. Each filter type will use a different technique appropriate to the specific filter's representation. Finally, we conclude with a discussion of the format for a popular sound file on the PC. We will consider how we can use sound files to investigate the characteristics of the filters we have designed.
The first decision to make when designing a system with a digital filter is whether an IIR or FIR filter should be used. Some of the advantages and disadvantages of each type have been discussed in the previous two chapters, so we will summarize those points here. First, and foremost, the correct filter type must be determined by the requirements of the application. IIR (recursive) filters have the advantages of providing higher selectivity for a particular order and a closed form design technique that doesn't require iteration. The design technique also provides for the rather precise solution to the specifications of gain and edge frequencies.
